All-perovskite-based polycrystalline thin-film tandem solar cells have the potential to deliver efficiencies of >30%. However, the performance of all-perovskite-based tandem devices has been limited by the lack of high-efficiency, low-band gap tin-lead (Sn-Pb)mixed-perovskite solar cells (PSCs).We found that the addition of guanidinium thiocyanate (GuaSCN) resulted inmarked improvements in the structural and optoelectronic properties of Sn-Pb mixed, low-band gap (~1.25 electron volt) perovskite films.The films have defect densities that are lower by a factor of 10, leading to carrier lifetimes of greater than 1 microsecond and diffusion lengths of 2.5 micrometers.These improved properties enable our demonstration of >20% efficient low-band gap PSCs.When combined with wider-band gap PSCs, we achieve 25% efficient four-terminal and 23.1%efficient two-terminal all-perovskite-based polycrystalline thin-film tandemsolar cells.
Bibliographical noteFunding Information:
The work at the National Renewable Energy Laboratory was supported by the U.S. Department of Energy (DOE) under contract DE-AC36-08GO28308 with Alliance for Sustainable Energy LLC, the manager and operator of the National Renewable Energy Laboratory. The work at the University of Toledo was partially supported by the Air Force Research Laboratory under Space Vehicles Directorate (FA9453-11-C-0253). We acknowledge support on perovskite synthesis and device fabrication and characterization from the DOE SunShot Initiative under the Next Generation Photovoltaics 3 program (DE-FOA-0000990); support on the transient reflection spectroscopy studies from the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the DOE Office of Basic Energy Sciences, Office of Science; and support on various structural and optoelectronic characterizations of perovskite thin films from the De-risking Halide Perovskite Solar Cells programof the National Center for Photovoltaics, funded by the DOE Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office.
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